Preemptive multi-skilled resource investment project scheduling problem: Mathematical modelling and solution approaches

•Preemptive multi-skilled resource investment project scheduling problem is studied.•The PMSRIP is mathematically formulated with and without level switch.•Two metaheuristic algorithms are proposed to tackle the PMSRIPs.•Effectiveness of the proposed algorithms is analyzed based on 94 test instances.

Many chemical production systems encounter with a functionally flexible workplace which need multi-skilled workers. This research integrates the multi-skilled project scheduling problem with the resource investment problem which aims to obtain concurrent optimal policy of project scheduling and skills' recruitment. The objective of the proposed model is minimization of total recruitment cost for different levels of the skills. An integer programming formulation is developed for the problem, and it is validated through solving several small scale instances using the GAMS software. To tackle real-life problem scales, a genetic-based and a particle-swarm-based algorithm with calibrated parameters and chromosome structures that guarantee feasibility are proposed. The performances of the solution procedures are evaluated by comparing the results obtained and the ones resulted by the GAMS software. In addition, the robustness of the algorithms' results for large scale instances is evaluated in different runs confirms the applicability of the proposed methodology.